Title: Daring Do and the Wrath of the Elementals!

Main characters: Daring Do, Rainbow Dash, the Mane Six, Ahuizotl.

Genre: Crossover, Alternate Universe, Comedy, & Adventure.

Crossover With: Crash Bandicoot: The Wrath of Cortex (sort of, while five of the villains from that game appear, none of the other main characters do.)

Premise:
During one her adventures, Daring Do tracks Ahuizotl down to an underground prison. She discovers him in the middle of an ancient ritual to resurrect in the ancient evil. She quickly attempts to stop him, however she ends up distrusting the spell that would bring the evil under his control. As a result, five powerful Elemental masks are upon Equestria:

Rok-Ko the Earth Elemental,
Wa-Wa the Water Elemental,
Py-Ro the Fire Elemental,
Lo-Lo the Air Elemental,
Uka-Uka the Master of Darkness.

Before she can stop them, the Elementals betray Ahuizotl and proceed to destroy the tomb in an attempt to bury them inside before teleporting away. However they manage to escape.

Ahuizotl reveals that the five masks were originally sealed away by a special warrior wielding the "Mask of Light". Due to the fact that he has more knowledge about the Elementals than she does, Daring Do is forced to make to a temporary truce with Ahuizotl in order to stop them.

They proceed to track them down, and it turns out-much to he shock-that they've not only attacked Ponyville of all places, but have also taken control of the Elements of Harmony themselves!

Rok-Ko possess Pinkie Pie,
Wa-Wa possess Applejack,
Py-Ro possess Rarity,
Lo-Lo possess Fluttershy,
and Uka-Uka possess Twilight.

Due to there being no masks to possess her, Rainbow Dash barely manages to escape the village and joins Daring Do on her quest. Now it's up to Daring Do, Rainbow Dash, and Ahuizotl to find the Mask of Light and stop the possessed mane five before they bring all of Equestria to ruin!